The invention relates to a feeding trough for a sliver opening device of an open-end spinning device.
Sliver opening devices for open-end spinning devices are known in various embodiments and have been extensively explained in numerous patent publications.
For example, German Patent Publication DE 35 01 842 C2 describes a sliver opening device wherein a cylindrical, preferably corrugated sliver draw-in cylinder with an associated feeding trough constitutes a gripping area for the feed sliver.
The slowly rotating sliver draw-in cylinder here feeds the feed sliver to a downstream-located opening roller at a constant transport speed.
This means that on its way to the opening roller the feed sliver, which is preferably stored in sliver cans, first passes through a condenser, which not only condenses the feed sliver, but also provides it with a definite, suitable profile for draw-in.
The condensed feed sliver subsequently enters the gripping area constituted by the sliver draw-in cylinder and the feeding trough, which customarily is wider than the feed sliver. It is assured in this way that the feed sliver is also dependably gripped in the edge areas.
To prevent the feed sliver from spreading out too far and to get into the edge areas of the opening roller where, because of the termination of the saw-tooth card set, dependable combing of the feed sliver is no longer assured, a fiber tuft support with lateral strips is arranged following the gripping area.
The lateral strips also prevent uncontrolled lateral excursions of the feed sliver because of the helically-shaped arrangement of the saw tooth card set.
However, there is a relatively large nip between the gripping area and the fiber tuft support in the feeding trough in accordance with German Patent Publication DE 35 01 842 C2.
Furthermore, sliver opening devices for open-end spinning devices, which have an additional pressure roller in the area of the feeding trough, are known from German Patent Publication DE 38 17 346 C2, for example.
This means that this known feeding trough has a gripping area constituted by a special pressure roller and a sliver draw-in cylinder, which is followed via an extensively rounded transition area by a concavely curved support surface for the fiber tuft.
Furthermore, lateral guide surfaces for the feed sliver are arranged in the transition area.
With this known feeding trough a relatively large, free nip exists between the gripping area and the fiber tuft support. Added to this is that, because of the convex curvature of the two transport rollers, only one nip line results, which is arranged clearly distanced from the opening roller because of the roller arrangement alone.
The above described feeding troughs have quite proven themselves when producing standard yarn, however, they show considerable disadvantages if so-called novelty yarns are to be produced.
Such novelty yarns have, for example, defined thickened places at recurring distances.
It is necessary for producing such a novelty yarn to periodically change the amount of individual fibers to be fed into the spinning rotor, this means that the sliver to be fed to the opening roller must be repeatedly accelerated and slowed down over short periods of time.
With known feeding troughs the problem exists in this connection, that the feed sliver backs up in the above explained open nip during the acceleration period, and is therefore combed-out only insufficiently, or in a delayed manner. Because of this, the desired effects are more or less blurred, which interferes greatly with the fabric.